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The health risks associated with the presence of heavy metals in drinking water can be severe. To address this issue, membrane separation technology is one of the consolidated alternatives. Inorganic, porous membranes were found in applications where low energy consumption is highly desirable. The selectivity of these membranes is attained by functionalisation. Graphene oxide functionalised membrane technology is promising for removing heavy metal ions. This work summarises, discusses and presents the relationship between adsorption and overall membrane separation process performance for heavy metal ions removal from wastewater when a graphene oxide-functionalised membrane is used. The separation performance depends on the hydrophobic interactions of the membrane and the solute. The electrostatic interaction between the negatively charged membrane surface and positively charged metal ions facilitates the adsorption, leading to the rejection of these metal ions. The influences of the chemical nature of the modifiers of graphene oxide layers are highlighted. [ABSTRACT FROM AUTHOR]

Hollow carbon fiber has a large surface area and a homogeneous pore structure which is required for adsorbents to remove metals in aqueous solutions. The physical properties of hollow carbon fiber can be modified and controlled by chemical activation and physical activation accompanied by a carbonation process using an inert gas. This study investigates the potential of the waste biomass of acacia leaves as a precursor to hollow carbon fiber. Acacia leaves were activated chemically with KOH 1 M before being subjected to one-stage integrated pyrolysis, which combines the carbonation process at 500 °C in an N2 gas environment with physical activation using a CO2 gas environment at 750 °C for 1 h. The samples were then characterized using the BET, SEM, and FTIR techniques. The resulting hollow carbon fiber had a significantly larger surface area (127.55 m2/g) than the raw acacia leaves. Subsequently, batch equilibrium experiments were carried out to evaluate the adsorption ability of hollow carbon fibers to remove Fe(II) from aqueous solutions at various dosages, contact times, and initial metal concentrations. Based on the isotherm studies and adsorption kinetics, the Langmuir with the maximum adsorption capacity, qm 14.11 mg/g, and pseudo-second-order models were found to be more suitable for this study. [ABSTRACT FROM AUTHOR]

A surface-modified mesoporous silica nanoparticle containing dimercaprol monomers was created utilizing the sol–gel condensation process, using tetraethyl orthosilicate (TEOS) as the silica source and poloxamer as the structure directing agent. To accomplish this synthesis, 3-glycidoxypropyl triethoxysilane (GPTS, 20 mol%) was incorporated into the silica walls during the sol–gel condensation process, along with TEOS. Furthermore, dimercaprol (DM) monomers were incorporated onto silica surfaces by a ring-opening reaction between GPTS epoxy groups, and dimercaprol hydroxyl groups. The prepared dimercaprol-modified silica adsorbent (MSN-DT NPs) material has been studied using a variety of instruments, including XRD, FT-IR, N2 adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric (TG) analysis, and zeta potential analysis. The MSN-DT NPs material selectively adsorbs mercury ions, with a high adsorption amount of 125 mg/g and a removal capability of roughly ~ 90% from the original metal ion mixture comprising other competing metals such as Pb2+, Ni2+, Fe2+, and Zn2+. The MSN-DT NPs adsorbent shows recyclable qualities for up to five cycles when treated with an acidic aqueous solution (0.1 M HCl). As a result, the MSN-DT NPs adsorbent may be regenerated and reused up to five times without losing its adsorption effectiveness. The experimental findings showed that the MSN-DT NPs adsorbent may be employed to selectively remove hazardous Hg2+ ions from an aqueous solution. [ABSTRACT FROM AUTHOR]

• Diatoms shaped by Si enrichment or low salinity accumulated more Cd and Cu. • Si-enriched cells under low salinity showed the highest instantaneous metal influx. • The adsorption capacity of diatoms is mediated by cell wall physicochemical traits. • Lower Si availability and salinity led to rougher cell walls with larger surface area. • Higher silicification level decreased cell surface potential with more silanol groups. Increasing nitrogen and phosphorus discharge and decreasing sediment input have made silicon (Si) a limiting element for diatoms in estuaries. Disturbances in nutrient structure and salinity fluctuation can greatly affect metal uptake by estuarine diatoms. However, the combined effects of Si and salinity on metal accumulation in these diatoms have not been evaluated. In this study, we aimed to investigate how salinity and Si availability combine to influence the adsorption of metals by a widely distributed diatom Phaeodactylum tricornutum. Our data indicate that replete Si and low salinity in seawater can enhance cadmium and copper adsorption onto the diatom surface. At the single-cell level, surface potential was a dominant factor determining metal adsorption, while surface roughness also contributed to the higher metal loading capacity at lower salinities. Using a combination of non-invasive micro-test technology, atomic force microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, we demonstrate that the diversity and abundance of the functional groups embedded in diatom cell walls vary with salinity and Si supply. This results in a change in the cell surface potential and transient metal influx. Our study provides novel mechanisms to explain the highly variable metal adsorption capacity of a model estuarine diatom. [Display omitted] [ABSTRACT FROM AUTHOR]

Nature-like technologies are being introduced into many human activities including mining wastewater treatment. This work is based on long-term studies of the Sibay copper-zinc-pyrite deposit development. It is dedicated to assessment of geochemical barriers effectiveness in Cu, Zn, Cd removal from water of the Karagayly River (receiving quarry and dump drainage water). The research is based on the elements’ content and forms in water and bottom sediments, pH values etc. Four types of hydrogeochemical environment (formed due to changes in the water use over the past 20 years) were distinguished using discriminant analysis. The mechanisms of barriers formation and destruction were described. Statistical modeling of the metals’ precipitation was performed by multivariate regression analysis. Cu is adsorbed by recently formed Fe hydroxides, and, to a lesser extent, precipitates with sulfates as water pH increases. Antagonism to Mn hydroxides has been demonstrated, due to different physicochemical conditions for their precipitation. Zn enters solid phase mainly with sulfates, this element also forms its own mineral phases. The second mechanism is adsorption by recently formed Mn hydroxides, which corresponds to the idea of similar conditions for the precipitation of metal hydroxides. Cd behavior reflects conditions intermediate between these of Cu and Zn. Contribution of both mechanisms (related to Fe hydroxides and aqueous sulfates) is equal. Antagonism to Mn is absent. According to the assessment results using of nature-like technologies in situ in watercourses, canals and other water drainage systems is promising. Developed statistical models can be used for needs of experimental studies and artificial geochemical barriers engineering.

Rapid growth in the industry has released large quantities of contaminants, particularly metal discharges into the environment. Heavy metal poisoning in water bodies has become a major problem due to its toxicity to living organisms. In this study, we developed a 3-chloropropyl triethoxysilane incorporated mesoporous silica nanoparticle (SBA-15) based adsorbent utilizing the sol–gel process and Pluronic 123 (P123) as a structure-directing surfactant. Furthermore, the produced SBA-15 NPs were functionalized with bis(2-aminoethyl)amine (BDA) using the surface grafting approach. The physical and chemical properties of the prepared SBA-15@BDA NPs were determined using a variety of instruments, including small-angle X-ray diffraction (SAXS), Fourier-transform infrared (FTIR), scanning electron microscope (SEM), N2 adsorption–desorption, thermogravimetric, particle size distribution, and zeta potential analysis. The MSN has a large surface area of up to 574 m2/g, a pore volume of 0.57 cm3/g, and a well-ordered mesoporous nanostructure with an average pore size of 3.6 nm. The produced SBA-15@BDA NPs were used to adsorb selectively to lead (Pd2+) ions from an aqueous solution. The adsorption study was performed under various conditions, including the influence of solution pH, adsorbent dose, adsorption kinetics, adsorption selectivity in the presence of competing metal ions, and reusability. The results of the kinetic study demonstrated that SBA-15@BDA NPs absorb selectively Pb2+ ions via chemisorption. The SBA-15@BDA NPs show Pb2+ ions with a maximum adsorption capacity of ~ 88% and an adsorbed quantity of approximately ~ 112 mg/g from the studied aqueous solution. The adsorption mechanism relies on coordination bonding between Pb2+ ions and surface-functionalized amine groups on SBA-15@BDA NPs. Furthermore, the proposed SBA-15@BDA NPs adsorbent demonstrated excellent reusability over five cycles without significantly reducing adsorption performance. As a consequence, SBA-15@BDA NPs might serve as an effective adsorbent for the selective removal of Pb2+ ions from aqueous effluent. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are global pollutants found in various environmental compartments, including oceans, freshwater bodies, soils, and air. Their persistence and potential to adsorb heavy metals raise significant concerns regarding water quality and ecosystem health. Understanding the interaction between MPs and heavy metals is crucial for assessing environmental risks and developing remediation strategies. In this study, we use electroanalytical techniques to investigate the adsorption of heavy metal ions— Cr³⁺, Zn²⁺, and Ni²⁺—by polystyrene MPs with different surface functionalizations: carboxyl, amino, and unfunctionalized. We conducted electrodeposition of metal ions on a gold ultramicroelectrode both before and after mixing with MPs. Following this, we used anodic stripping voltammetry to measure the change in the electrodeposited charge (ΔQ). This charge difference, observed before and after the interaction of ions with MPs, was analyzed to understand the adsorption kinetics and dynamics. Our experiments revealed that carboxyl-functionalized MPs exhibited the highest ΔQ due to strong electrostatic attraction with the metal ions, with values 1.67 ×, 1.50 ×, and 1.22 × greater than those for amino-MPs for Cr³⁺, Zn²⁺, and Ni²⁺, respectively. Amino-MPs displayed considerable ion adsorption, suggesting poor electrostatic repulsion between two positively charged entities. Interestingly, unfunctionalized MPs, which had a negative surface charge similar to carboxyl-MPs, showed different adsorption characteristics, with lower ΔQ values for all metal ions. This study underscores the significant role of surface functionalization on the adsorption efficiency and kinetics of heavy metal ions by MPs. It also demonstrates the utility of electroanalytical techniques in understanding metal ion-MP interactions, offering insights into potential environmental impacts and remediation strategies, as well as in developing electrochemical sensors for detecting heavy metal ions adsorbed on MPs.

Adsorption is the most efficient technique for the removal of toxic organic dyes and metal ions from wastewater and it demands efficient, low-cost, environment friendly and collectable adsorbents. In this study, a one-pot strategy has been developed for the crosslinking of chitosan and carboxymethyl cellulose with citric acid to form the cross-linked hydrogel. The synthesized biosorbent hydrogel was characterized by FTIR, XRD and SEM that have confirmed the successful crosslinking. The batch adsorption experiments were performed to examine the capacity of hydrogel for the adsorption of Cu(II). The optimization of the adsorption process was carried out on the basis of various factors including; metal ion concentration, time, temperature, pH, agitation speed and adsorbent dose. Different isothermal and kinetic models were applied to interpret the data. The thermodynamic studies revealed that Langmuir model was the best fit with > 90% Cu(II) removal at pH 6. The kinetic studies confirmed the suitability of pseudo-second-order kinetics with correlation coefficient (R2) value 1. Several adsorption–desorption cycles were performed to check the recovery and reusability of hydrogel without the loss of maximum adsorption capacity. [ABSTRACT FROM AUTHOR]

This work evaluates the efficiency of three biochar samples toward the adsorption of manganese, iron, and selenium present in a sample of urban wastewater. The biochar was produced from the pyrolysis of rice husks at 350 °C for 6 h (RHB) and subsequently modified using HCl (RHBHCl) or NaOH (RHBNaOH) to increase its surface area. The RHBNaOH sample exhibited the highest removal efficiency for the three metals. The metals' adsorption removal efficiency for RHBNaOH was in the order Mn (76%), Se (66%), and Fe (66%), while for RHBHCl, it was Fe (59%), Mn (30%), and Se (26%). The results show that the as-prepared RHB can remove the metals, even if in low amounts (Fe (48%), Mn (3%), and Se (39%)). The adsorption removal for the three types of adsorbents follows the Langmuir isotherm model. Pseudo-first-order and pseudo-second-order models were used to determine the adsorption mechanism for each of the three adsorbents. Both models showed a good fit with R2 (>0.9) for the RHBNaOH and RHB sorption of Fe, Mn, and Se. Overall, this work demonstrates the potential of biochar for the removal of metals from real wastewater. [ABSTRACT FROM AUTHOR]

Polyamide dendrimers, poly(vinyl alcohol) (PVA), and poly(acrylic acid) (PAA) were heat-treated for hydrogels films preparation. The effect of the dendrimers periphery type (OH, NH2), dendrimers content, and generation number on the properties of the hydrogels and adsorption performance at different pHs have been examined. Chemically bonded dendrimers into the hydrogel showed a high swelling ratio and high gel content compared to a neat film of PVA/PAA. The incorporation of dendrimers increases the swelling ability of the hydrogel. The highest swelling obtained was at low dendrimers content and high generation numbers G3-OH and G3-NH2. The diffusion of water within the hydrogel follows the Fickian character. Combining the polyamide dendrimers into the hydrogel films showed potential use in metal chelating and the adsorption of Ni2+, Zn2+, Fe2+, and Cu2+ ions onto the hydrogel. The adsorption results have shown dependency on pH, generation number, and dendrimers content. The adsorption increases at pH 6, high generation number, and high dendrimers content regardless of the periphery. The hydrogel containing G3-OH had high swelling and metal ion adsorption. [ABSTRACT FROM AUTHOR]

Ethylenediaminetetraacetic acid (EDTA) is a well-known metal chelator and an attractive ligand for covalently modifying adsorbents for bioremediation. Cellulose, a naturally occurring biopolymer, has immense potential as an inexpensive, earth abundant, biocompatible scaffold for EDTA-facilitated environmental remediation; however, pretreatment of the material is required to achieve sufficient degrees of chemical modification. In this study, Natural Fiber Welding (NFW) is used to prepare commercial cotton Aida cloth for EDTA functionalization. Following NFW, the cotton scaffold was covalently modified with up to 0.56 mmol of EDTA per gram of adsorbent, a nearly 2.5-fold increase over native material. The welded EDTA-modified substrates were tested qualitatively against cobalt and quantitatively against nickel, reaching equilibrium binding capacities (qe) of up to 46 mg metal per g of adsorbent, on par with capacities reported from past work on EDTA-modified cellulose. In addition, adsorbent material could be regenerated using mild acid treatment with no significant loss in qe. Unlike the controls, the fiber-welded EDTA-Aida did not fray even after 3 chelation cycles, indicating enhanced textile robustness afforded through NFW treatment. Overall, NFW offers a new approach to converting commercially available, sustainable biomaterials into robust adsorbents for environmental remediation.

In this study, polyester dendrimers based on triethanolamine were synthesized via a multi-step divergent approach. Triethanolamine was reacted with sebacoyl chloride and 1,4-butanediol as repeating units. The synthesized dendrimers up to G6.5 were characterized by FTIR, 1H-NMR. The incorporation of selected generations G2.5, G4.5 and G6.5 dendrimers into PVA/PAA films and the influence of added dendrimers on the properties of the films were investigated. The results showed the gel content increased with an increase in the dendrimers content and generation number. The incorporation of dendrimers increases the swelling ability of the films. The highest swelling obtained was at low dendrimers content 1 w% and highest generation number G6.5. The films exhibited pH-sensitive behaviors where they decrease at low pH and expanded at pH 10. The ability of metal adsorption Fe2+, Cu2+, Ni2+ and Zn2+ was investigated, the addition of dendrimers enhanced the film adsorption, and the adsorption capacity increased with the increase in pH. The antimicrobial activity of the polyester dendrimers G2.5, G4.5 and G6.5 was investigated, against gram-positive Staphylococcus arouse (S. arouse) and gram-negative Escherichia coli (E. coli) bacteria. The results showed that G6.5 had the highest antimicrobial activity against S. arouse. [ABSTRACT FROM AUTHOR]

The current study reports batch studies using eucalyptus wood waste derived biochar (EWB) to adsorb Cr(VI) and Cu(II) from aqueous solutions. Scanning electron microscopy, specific surface analysis, and Fourier-transform infrared spectroscopy were used to study the morphology and structure of the EWB. A thorough analysis of the variables affecting adsorption performance was conducted. The Freundlich isotherm, Langmuir isotherm, pseudo-second-order, and pseudo- first-order models were used to study the adsorption process. The optimal conditions for the highest adsorption of Cr(VI) and Cu(II) as of aqueous solution on the EWB adsorbents were found to be an initial concentration of 30 ppm, contact time of 60 min, temperature of 60°C, adsorbent dose of 0.20 g, and 3, 6 pH. The adsorption system, according to kinetic studies, follows a pseudo- second-order equation. It was shown that the experimental results for the adsorption of Cr(VI) and Cu(II) on EWB were best suited by the Langmuir equation. The trial results revealed that the highest adsorption at optimum condition for Cr(VI) and Cu(II) from aqueous medium was 96.23% and 98.46%, respectively. The produced EWB have a high adsorption capacity (>95%) and a porous structure that make them very attractive as an alternative to Cr(VI) and Cu(II) adsorbents. [ABSTRACT FROM AUTHOR]

Heavy metal pollution is a global problem affecting the environment and human health. Sediment is the source sink of heavy metals in water. Under certain circumstances, the migration of heavy metals will cause water pollution. Therefore, it is of great significance to study sediment composition and composite complexes in the migration and transformation of heavy metals. To understand the adsorption mechanisms of composite complexes and improve the theoretical understanding of adsorption in multi-component complex systems, this study explored the characteristics and rules of Cu adsorption to organic–inorganic, inorganic minerals, and iron-oxide–clay complexes in the estuary sediments of the Dianchi Lake. The Langmuir and Freundlich isotherm models were used for Cu adsorption experiments on three complexes to study their adsorption kinetics. X-ray diffraction and Fourier transform infrared spectroscopy characterized the samples before and after adsorption. The relationship between adsorption capacity and sediment composition was analyzed through redundant analyses. The results showed that the Freundlich isothermal model was better than the Langmuir model in describing the adsorption behavior of the adsorbents. The contribution of iron and aluminum oxides to Cu adsorption was more than that of organic matter. The organic–inorganic complexes functional groups involved in copper adsorption are the most, which resulting in a higher adsorption capacity. The organic matter removal (organic degradation in sediment) will reduce the polar functional groups and reduce silicide activity, leading to heavy metal desorption and re-entry into the water body. [ABSTRACT FROM AUTHOR]

Charged biopolymers able to adsorb solubilized metal cations instead of precipitating them as inorganic waste provide a sustainable option for conventional lime treatment of acidic metal-bearing effluents. We investigated the adsorption of trivalent iron (Fe3+) and lanthanum (La3+) on anionic TEMPO (2,2,6,6-tetramethyl-piperidine-1-oxyl)-oxidized nanofibrillated cellulose (TONFC) from concentrated solutions at increasing ionic strengths (I). In the adsorption experiments, solutions containing 25–150 mM FeCl3 or LaCl3 as such (I0), or with I adjusted to 1 (I1) or 4 (I4) with NaCl, were treated with TONFC. Following filtration, the solutions were subjected to pH measurement and analysis for the TONFC-induced changes in Fe and La concentrations. The susceptibility of the retained metals to desorption was elucidated by back extraction. Adsorption of Fe3+ and La3+ significantly exceeded the negative charge density of TONFC, which led to positive overcharging of cellulose fibrils. The consequent Coulomb repulsion between the fibrils prevented their aggregation and enabled metal retention even under highly acidic conditions. At high I, Na + ions derived from the NaCl background were unable to compete with Fe3+ or La3+ for the sorption sites. Excess of Cl- ions, in turn, produced chloride complexes, particularly with Fe3+. They abated overcharging, which induced TONFC condensation and reduced Fe sorption within a critical concentration range. Above this range, Fe sorption recovered presumably due to partial redispersion of cellulose fibrils. Analogous condensation and redispersion of TONFC was not detected in the reaction with La3+. In conclusion, its overcharging tendency renders TONFC a superior agent for the treatment of highly concentrated metal-bearing effluents of very low pH. Successful utilization of the material as a water purification agent, however, requires understanding of the re-entrant behavior of TONFC with solutions of high I.

Stenotrophomonas rhizophila JC1 and its extracellular polysaccharides (EPS) have been shown to effectively adsorb heavy metals in previous studies. The fermentation conditions of EPS by S. rhizophila JC1 were optimized using the Box-Behnken design (BBD). The composition, structural characteristics, and heavy metal adsorption capacity of EPS were systematically evaluated. The alleviation mechanism of Pb2+ stress on alfalfa was investigated through EPS inoculation. The maximum EPS yield reached 0.313 %. EPS consisted of glucose, glucosamine, galactose, and mannose in a molar ratio of 12.20:1:22.29:1.68. EPS also contained four distinct polymers with molecular weights of 623,683.71 Da, 144,072.27 Da, 105,892.21 Da, and 51,094.79 Da. The adsorption processes conformed to the pseudo-second-order model and Langmuir isotherm model. High Pb2+ concentrations significantly reduced germination percentage, germinative force, root length, fresh weight, and soluble protein, inhibited photosynthesis, exacerbated oxidative stress, and caused damage to the antioxidant system, thereby inhibiting seedling growth. EPS at low concentrations can promote alfalfa seed germination and mitigate Pb2+ stress by reducing the aforementioned damage. This study highlights the potential of EPS in soil remediation and enhancing plant resistance to heavy metal stress. • Fermentation conditions of exopolysaccharides from S. rhizophila JC1were optimized. • The structure and physicochemical properties of EPS were studied. • The EPS exhibited high adsorption capacity of Pb2+ and plant growth promotion ability. • The mechanism of EPS alleviating the toxicity of Pb2+ to alfalfa was explored. [ABSTRACT FROM AUTHOR]

• Determined molecular-level interaction mechanisms controlling the adsorption of metal ions onto algal biochar. • Identified key functional groups responsible for enhanced metal-ion adsorption of algae biochar. • Affinity of algal biochar toward Cu²⁺ was the highest, followed by Fe²⁺ and Zn²⁺. This paper introduces a biogenic adsorbent derived from microalgae to immobilize copper, iron, and zinc. The adsorbent is made through hydrothermal liquefaction of Cyanidioschyzon merolae to form biochar. We used density functional theory (DFT) and laboratory experiments to elucidate the molecular interactions responsible for metal adsorption onto algal biochar. UV–Vis spectroscopy confirmed metal-ion adsorption independent of solution pH, and thermogravimetric analysis revealed changes in thermal stability, indicating chemical interactions between biochar and metal ions. The dominant mechanisms of adsorption were identified as cation-π interactions, complexation, and ion exchange. The stability of the adsorption at various pH and temperatures suggest strong binding affinity. Our DFT analysis showed competitive adsorption with the order Cu²⁺ > Fe²⁺ > Zn²⁺, displacing inherent cations such as K⁺. Algal biochar shows promise as an additive in geopolymer alongside mine tailings to address concerns about heavy-metal leaching, especially in construction elements exposed to water. The study outcomes promote sustainability, resource conservation, and the prevention of environmental pollution. [Display omitted] [ABSTRACT FROM AUTHOR]

Streams are regarded as a pathway for spreading microplastics from land to various aquatic systems. The contamination of streams connected to the Rawa Jombor Reservoir may increase microplastic concentrations in the reservoir. The water coming out of the reservoir carries microplastics that spread out into the stream networks around the reservoir. Heavy metals have a high affinity for microplastics, increasing metal burdens on the surface of microplastics. The transfer of microplastics along the food chain leads to the possibility of increased adverse effects on organisms, mainly top predators. This research evaluated the accumulation and characterization of microplastics in water, sediment, and aquatic fauna (zooplankton, benthos, and fish); interactions with heavy metals (Pb, Cu, Cd, and Zn); and health risk assessment. Microplastics were collected from six sampling locations. The density, type of polymers, and color of microplastics were analyzed, as well as heavy metal concentrations on the surface of microplastics and a health risk assessment. The results showed microplastic contamination at a moderate level. The accumulation of microplastics in aquatic fauna showed the same pattern as microplastics in the environment. Microplastic concentrations in aquatic fauna showed an increase through trophic transfer and indications of biomagnification. Heavy metals were adsorbed on the surface of microplastics in high concentrations. Based on the health risk assessment, microplastic contamination of fish at the inlet and outlet of the Rawa Jombor Reservoir is still safe, but further monitoring is needed because of the possible long-term health hazards that may arise.

The synthesis, characterization and evaluation of cellulose-graft-poly(4-vinylpirydine) for heavy metal removal from wastewater, is reported. Cellulose was obtained from a corn cob biomass using a recently developed gas-phase acid pretreatment process (GPAPP). The obtained corn cob cellulose (CCC) was functionalized by partial esterification of the superficial -OH groups with α-bromoisobutyryl bromide (BIBB) under mild conditions (room temperature and dimethyl formamide, DMF as solvent). The functionalized cellulose was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The BIBB-functionalized CCC was used as initiator for surface-initiated (SI) atom transfer radical polymerization (ATRP) of 4-vinylpyridine (4VP). Grafting of the polymer (p4VP) onto cellulose was confirmed by FTIR, TGA and XPS. The same procedure was carried out with microcrystalline cellulose (MCC) as a reference. The performance of the cellulose copolymers for the removal of lead and iron from water was evaluated. Removal percentages of 83 % in 30 min for lead and 79 % in 180 min for iron were obtained with MCC-g-p4VP. In contrast, removal percentages of 50 % were obtained in 30 min for lead and 30 % for iron in 180 min, respectively, when CCC-g-p4VP was used., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Chitosan is a well-studied biomaterial which has been widely used for environmental applications as an efficient natural polymer for the adsorption and removal of metal ions. Owing to its unique properties, chitosan shows good metal-binding behavior toward several different metal ions such as Cu2+, Zn2+, Cd2+, Ni2+, Co2+, and Ca2+. Chemical modifications with the introduction of functional groups have been carried out extensively and thereby producing various chitosan derivatives to increase the selectivity and adsorption capacity toward metal ions. The present work focuses on two such monofunctional derivatives, namely, carboxymethyl chitosan (CMC) and ethylenediaminetetraacetic acid chitosan (EDTA-CS) which have been recognized as excellent adsorbents for metal removal. The main objective of this study was to synthesize a new bifunctional chitosan derivative, namely, ethylenediaminetetraacetic acid–carboxymethyl chitosan (EDTA-CMC) by attaching both carboxymethyl and EDTA functional groups on the polymer backbone and thereby enhancing its metal-binding properties. The bifunctional derivative synthesis was conducted by combining the procedures of synthesis of CMC and EDTA-CS. Newly synthesized EDTA-CMC derivative was characterized by Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscope analysis, and thermogravimetric analysis. Adsorption properties of EDTA-CMC were investigated with Cu2+ ions which produced an adsorption capacity of 111.90 mg g−1 for 1000.0 mg/L and 12.20 mg g−1 for 10.00 mg/L Cu2+ solutions. The preliminary results revealed that EDTA-CMC is an effective adsorbent than CMC to remove Cu2+ in aqueous samples. The effects of pH, initial concentration, and mass of the adsorbent in the adsorption process were studied. Under the optimized parameters of an adsorbent dosage of 10.00 mg and pH 5.5, a comparable maximum adsorption capacity up to 112.44 mg g−1 was achieved with a 150.00 mg/L of Cu2+ solution. Furthermore, EDTA-CMC showed good adsorption performance even after five cycles of regeneration. [ABSTRACT FROM AUTHOR]

In the present study, an adsorbent with a synergistic effect was developed from chitosan (CS) and Fe3O4 nanoparticles (Fe3O4 Nps) to remove Cr(VI) from aqueous solutions. The Fe3O4 Nps were synthesized by co-precipitation and were characterized by TEM. The CS/NPs composites were prepared by electrospinning technique and analyzed by SEM, FT-IR, DSC, and TGA. In the batch system, the influence of Fe3O4 Nps content, pH, contact time, Cr(VI) initial concentration, adsorbent dosage, and the temperature was investigated; the Cr(VI) concentration was determined using a colorimetric method by UV–Vis spectroscopy. The Fe3O4 Nps presented a quasi-spherical shape and an average size of 18 nm, with a low particle distribution. The SEM analysis reveals the presence of highly porous, interconnected micrometric structures. The optimal adsorption conditions were 1% load of Fe3O4 Nps by weight of CS, pH 3, 25 °C, and equilibrium was reached at just 9 min. Besides, the adsorption is favored by increasing Cr(VI) initial concentration and adsorbent dosage. The studies of reaction kinetics and adsorption equilibrium showed that the experimental data were better fitted to the Pseudo-second-order and Langmuir isotherm models, establishing monolayer formation and chemisorption. The maximum adsorption capacity of CS/Fe3O4 Nps was 440.75 mg/g, which indicates a high affinity of the adsorbent for Cr(VI). Finally, a kinetic diffusion study established that intraparticle diffusion, and in particular surface diffusion, are important resistances in the transport of Cr(VI) from the liquid phase to the active site. [ABSTRACT FROM AUTHOR]

Streams are regarded as a pathway for spreading microplastics from land to various aquatic systems. The contamination of streams connected to the Rawa Jombor Reservoir may increase microplastic concentrations in the reservoir. The water coming out of the reservoir carries microplastics that spread out into the stream networks around the reservoir. Heavy metals have a high affinity for microplastics, increasing metal burdens on the surface of microplastics. The transfer of microplastics along the food chain leads to the possibility of increased adverse effects on organisms, mainly top predators. This research evaluated the accumulation and characterization of microplastics in water, sediment, and aquatic fauna (zooplankton, benthos, and fish); interactions with heavy metals (Pb, Cu, Cd, and Zn); and health risk assessment. Microplastics were collected from six sampling locations. The density, type of polymers, and color of microplastics were analyzed, as well as heavy metal concentrations on the surface of microplastics and a health risk assessment. The results showed microplastic contamination at a moderate level. The accumulation of microplastics in aquatic fauna showed the same pattern as microplastics in the environment. Microplastic concentrations in aquatic fauna showed an increase through trophic transfer and indications of biomagnification. Heavy metals were adsorbed on the surface of microplastics in high concentrations. Based on the health risk assessment, microplastic contamination of fish at the inlet and outlet of the Rawa Jombor Reservoir is still safe, but further monitoring is needed because of the possible long-term health hazards that may arise. [ABSTRACT FROM AUTHOR]

Development of nanofilters with the ability to remove toxic metal ions from effluent wastewater will be of immense help to the leather industry. In this study, fibrous nanofilter (FNF) was prepared using microfibrillated cellulose and tea leaf microparticles blended in poly (vinyl) alcohol. FNF was analysed for its efficacy to remove hazardous metals from tannery effluent wastewater. The FNF had promising traits of tensile strength (19.24 + 0.05 Mpa), elongation at break (22.31 + 0.12%), flexibility (10.88 + 0.05%), water absorption (37.86 + 0.14%) and desorption (32.54 + 0.33%). The metal adsorption studies clearly reflected the removal of toxic Cr (VI) ions from the effluent water by FNF. The study establishes an economically feasible and highly efficient way to remove hazardous metal ions from effluent wastewater. [ABSTRACT FROM AUTHOR]

Macrocyclic calixarene compounds exhibit versatile properties, which have been employed for the complexation, extraction, and transport of various metal ions. However, the potential applications of calixarenes are not straightforward. This review includes the "structural effects" of calixarene derivatives and the concept of adsorbent design incorporating calixarene derivatives after a brief introduction on the molecular design of calixarene derivatives used as extraction reagents. The adsorbents incorporating calixarene moieties are classified into four types and examples of metal adsorption using a variety of adsorbents are also introduced. [ABSTRACT FROM AUTHOR]

The contamination of wastewater with metals and the use of biotechnologies to remove them is commonly discussed in theoretical biology, microbiology and biotechnology classes aimed at undergraduate students. This work introduces an easy, economical and safe practical laboratory class related to this topic. The practice consists in performing batch assays to remove Al(III) from aqueous solutions by using non-viable bacterial biomass trapped in agar-agar beads. Students prepare these beads and analyse Al(III) adsorption on the basis of: pH, time of contact, and Al(III) concentration. Free Al(III) is quantified spectrophotometrically through a simple colorimetric method. The data obtained are used to calculate and graphically represent the amount of metal adsorbed to the beads. Finally, students analyse and discuss the results to determine the optimal adsorption conditions. Moreover, since Al(III) becomes much more attached to beads with trapped biomass than to beads without microorganisms, the class serves to demonstrate one of the advantages of using immobilised microbial cells in adsorption processes. This class was satisfactorily implemented in an upper-level course for undergraduate students of biological sciences. They were able to properly execute all the experiments and calculations proposed and to become acquainted with useful experimental design to remove a metal. [ABSTRACT FROM AUTHOR]

Glomalin-related soil protein (GRSP), a ubiquitous microbial product, plays a crucial role in particle aggregation and metal adsorption, but the underlying mechanisms remain unknown. Here, GRSP fraction was extracted from estuarine ecosystems and systematically characterized to elucidate the aggregation mechanisms and its impact on coastal environment improvement. We found that GRSP fraction (gravimetric mass of extracted GRSP, 5.1–24.3 mg g−1) was a globally relevant novel bioflocculant and that protein (linked to Bradford protein assay, 1.64–4.37 mg g−1) was the active flocculant constituent. The zeta potential, FTIR, XPS, and 13C NMR analyses identified its key constituents and structure, and revealed that the charge neutralization and bridging were GRSP fraction aggregation mechanisms. Thermogravimetric-infrared spectrometry analysis showed that GRSP fraction was highly thermostable, and the main volatile pyrolysis products included H2O, CO2, CO, and CH4. The SEM-EDX and XPS Fe valence spectroscopy suggested that GRSP fraction contained rich Fe (11.91 ± 0.48%) and could form Fe-rich flocs with particles. We also found that GRSP fraction has a high adsorption capacity (76–95%) for Cu, Zn, Pb and Cd, and its flocculation properties provide new insights into metal adsorption. The analysis of particle aggregation mechanism and its metal adsorption capacity is of great significance to elucidate the role of GRSP fraction in coastal environment improvement.

In this study, green tea waste (GTW) was used to synthesize the iron oxide (IO) nanoparticles (IO@GTW) to facilitate the adsorption of heavy metals from wastewaters. To satisfy structural integrity needs, the synthesized IO@GTW was incorporated into a polyvinyl alcohol (PVA)/alginate polymer network to obtain PVA/alginate/IO (PAI) hydrogels. Experimental techniques of transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) were subsequently used to confirm the successful synthesis of IO nanoparticles. Scanning electron microscopy (SEM) established the porous microstructure of PAI hydrogels, while FT-IR analysis revealed the physical incorporation of IO@GTW in PAI hydrogels. The adsorption of Cu2+ and Cr6+ on PAI hydrogels was subsequently investigated. The present study was able to show that the removal ratio and adsorption capacity of the synthesized PAI hydrogels depended on the pH, initial concentration of metal ions in the solution, and contact time. The equilibrium isotherms of Cu2+ and Cr6+ adsorption were well-described using Langmuir and Freundlich isotherm models. The adsorption kinetics of Cu2+ can be modelled using the pseudo-second-order model, and the adsorption kinetics of Cr6+ can be modelled using both pseudo-first-order and intraparticle diffusion models. This study, therefore, demonstrates the functionality of integrating green tea waste in a polymeric composite to perform as an effective and green adsorbent for heavy metal removal, thus indicating the viability of its future application in wastewater treatment operations.

This work describes the preparation and use of a polydimethylsiloxane sponge amino functionalized for the adsorption of copper in water. The sponge was structurally characterized by infrared spectroscopy and solid-state 29Si NMR, which indicated the presence of silsesquioxane units that acted as nodes on the PDMS chains and linked the functional groups to the network. Thermogravimetric analysis of the product showed good thermal stability, with the initial temperature of weight loss at 400 °C. The material displayed a high degree of swelling in polar solvent, presumably due the cavities. The presence of the amino group increases the adsorption of copper onto the surface of the sponge, with adsorption capacity of about 2.0 mmol (127 mg) per gram of material. The sponge shows promising results for environmental remediation with the removal of copper in water, as well as a simple utilization with no need of a separation process after metal adsorption. Highlights: A polydimethylsiloxane sponge functionalized with amino groups was prepared. Through a single step preparation process. Adsorption equilibrium are reached after 72 h immersion in aqueous solution. Copper ions was absorbed efficiently from water solution, on the sponge. High adsorption capacities in aqueous media. [ABSTRACT FROM AUTHOR]

This study utilizes density functional theory (DFT) with the Lanl2dz functional to investigate the effect of silver (Ag), gold (Au) and palladium (Pd) metal adsorption on the electronic properties of graphene oxide (GO). The studied structures, which are pristine GO, Ag-GO, Au-GO, and Pd-GO, are labeled as R (reference), X1, X2, and X3, respectively. The geometrical optimization indicates that Au forms a physical bond with a carbon atom on GO with a bond length 2.169 Å. While, the GO exhibited an energy band gap of approximately 2.39 eV, the subsequent adsorption of metals Ag, Au and Pd leads to a decrease in the band gap, with values of 2.07 eV for X1, 2.16 eV for X2, and 2.28 eV for X3. Further analysis reveals significant differences in the electronic properties of the various materials. Compared to the dipole moment of R (∼8.66 D), the dipole moment of X1-X3 ranged from 2.55 D to 6.11 D, which is lower than R. Our study reveals a modification in the charge distribution within the molecules upon metal adsorption. Interestingly, the open circuit voltage (V OC) exhibits a trend where X2 (1.72 eV) > R (1.16 eV) > X3 (0.95 eV) > X1 (0.54 eV). These findings highlight the crucial role of dopant selection in tuning the optoelectronic properties of GO. By carefully choosing dopants, we can optimize the optoelectronic properties of GO, making it suitable for various applications, including solar energy conversion. [Display omitted] [ABSTRACT FROM AUTHOR]

Herein, we demonstrate the prospects of tackling several environmental problems by transforming a local rice husk residue into an effective adsorbent, which was then applied for the treatment of real landfill leachate (LL). The study focused on establishing (i) the effect of simple washing on morphological aspects, (ii) evaluating target adsorption capacity for total iron (Fe) and nickel (Ni), (iii) determining regeneration and reuse potential of the adsorbent and (iv) complying to the requirements of worldwide legislations for reuse of treated LL wastewater. The adsorbent was prepared by employing a simple yet effective purification process that can be performed in situ. The LL was collected post-membrane treatment, and the characterizations revealed high concentrations of Fe, Ni, and organic matter content. The simple washing affected the crystallinity, resulting in structural alterations of the adsorbents, also increasing the porosity and specific surface. The adsorption process for Ni occurred naturally at pH 6, but adjusting the pH to 3 significantly improved removal efficiency and adsorption capacity for total Fe. The kinetics were accurately described by the pseudo-second-order model, while the Langmuir model provided a better fit for the isotherms. The adsorbent was stable for 5 reuses, and the metals adsorbed were recovered through basic leaching. The removal capacities achieved underscore the remarkable effectiveness of the process, ensuring the treated LL wastewater meets rigorous global environmental legislations for safe use in irrigation. Thus, by employing the compelling methods herein optimized it is possible to refer to the of solving three environmental problems at once. [Display omitted] • Simple and effective adsorbent production that can even be performed in situ. • Simple washing process resulted in a structured and homogeneous surface. • Adsorption occurs in monolayer through complexation and electrostatic interactions. • AC-T is highly reusable and selective towards the removal of Fe and Ni. • Treated LL sample in compliance with strict environmental legislation for reuse. [ABSTRACT FROM AUTHOR]

Uniformly-sized porous cellulose beads functionalized with amidoxime groups were prepared for the first time using a microfluidic method with N-methylmorpholine N-oxide (NMMO) monohydrate as a cellulose solvent. The molten state cellulose dope in NMMO monohydrate (cell/NMMO dope) as a disperse phase and hot mineral oil as a continuous phase were used in a T-junction microfluidic chip to produce uniformly-sized cell/NMMO droplets. Coagulation of the molten state cell/NMMO droplet at high temperature and amidoxime functionalization could prepare the highly-porous spherical amidoxime-functionalized cellulose beads with a uniform fibrous open internal structure. The prepared amidoxime-functionalized cellulose beads showed excellent metal adsorption properties with a maximum adsorption capacity of ~ 80 mg g−1 in the case of Cu2+/phthalate ions. The newly developed highly-porous cellulose beads can open many new applications with other proper functionalization at the reactive hydroxyl groups of the cellulose. [ABSTRACT FROM AUTHOR]

In this study, we propose a green and environmentally-friendly method to extract hydroxyapatite (HAP) from crucian carp scales by a deep eutectic solvent (choline chloride/1,4-butanediol). The optimal conditions for the extraction were as follows: an extraction temperature of 65 °C, an extraction time of 2 h, and a solid:liquid ratio of 1:15 (g:g). Under these conditions, the extraction rate of HAP was 40.58% ± 0.14%. The functional groups and crystallinity of the hydroxyapatite obtained were analyzed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The chemical composition was determined by energy dispersive X-ray spectrometry (EDX) and inductively coupled plasma emission spectrometry (ICP-MS). The surface morphology and particle size distribution were observed by scanning electron microscopy (SEM). The thermal stability was analyzed by thermogravimetric analysis (TGA). The adsorption capacity was determined by metal ion adsorption experiments. The results show that the extracted HAP has a heterogeneous morphology and is a mixture of the phosphates of carbonic acid and phosphoric acid, with high purity and excellent thermal stability. HAP has a good adsorption capacity for metal ions such as lead, copper, silver, and zinc. Image 1 [ABSTRACT FROM AUTHOR]

In this study, the production and compositional analysis of exopolysaccharides produced by Bacillus cereus KMS3-1 grown in metal amended conditions were investigated. In addition, the metal adsorption efficacy of exopolysaccharides (EPS) produced by KMS3-1 strain was evaluated in a batch mode. Increased production of exopolysaccharides by KMS3-1 strain was observed while growing under metal amended conditions (100 mg/L) and also, the yield was in the order of Pb(II)>Cu(II)>Cd(II)>Control. Characterization of EPS using FT-IR, XRD, and SEM analysis revealed that the EPS can interact with metal ions through their functional groups (O‒H, CH, C˭O, C‒O, and C‒C˭O) and assist the detoxification process. Further, equilibrium results were fitted with the Langmuir model and notably, the maximum adsorption capacity (Qmax) of EPS for Cd(II), Cu(II), and Pb(II) found to be 54.05, 71.42, and 78.74 mg/g, respectively. To the best of our knowledge, EPS demonstrating proficient metal adsorption was substantiated by XRD analysis in this study. Owing to good adsorbing nature, the exopolysaccharides could be used as chelating substances for wastewater treatment.

Field-scale experiments were conducted to assess biochar's ability with and without supplements to sequester heavy metals of lead (Pb2+) and zinc (Zn2+) from stream water contaminated by abandoned mines. The study was conducted at the Frongoch mine watercourse site in central Wales for 1104 h (46 days). The methods employed include pyrolysis of waste Leylandii feedstocks at 700 °C and post-amendment ash at ratios in mass (kg/kg) 1:10, 1:35, 1:50, and 1:100 of biophos to biochar (BC) and 1:1:100 mixed biophos and cockleshell ash to biochar (CBB). The collected data were analyzed by ASTM Brunauer-Emmett-Teller (BET), XRF spectrometer, R-stat, and SPSS statistical procedures. The results showed that non-amended samples are better suitable as adsorbent materials of lead and zinc. Overall, this field study showed that 33 g/kg of lead and 30 g/kg of zinc could be sequestered by 50 g of biochar (BC) and activated carbon (AC) from the contaminated mine watercourse containing 0.62 mg/L and 15.8 mg/L of lead and zinc metals flowing at 0.014 m3/s. These adsorbent materials BC and AC applications are variably recommended at an optimal replacement interval of 1104 h (46 days) and 72 h (3 days) for lead and zinc sorption, respectively. [ABSTRACT FROM AUTHOR]

In this study, an alumina modified onion skin (AMOS) composite was synthesized, characterized, and used as an adsorbent to remove Pb2+ and Cd2+ from aqueous solutions via adsorption process. The central composite design was used for the optimization of metal ions adsorption on AMOS. The experimental data were analyzed using equilibrium isotherm and kinetic models. Predicted values of removal efficiency were found to be in good agreement with the observed values obtained (R2 = 0.9612 for Pb2+ and R2 = 0.8616 for Cd2+). The results obtained showed that at the optimum conditions of 200 mg/L initial metal ions concentration, 1.20 g/L adsorbent dosage, and 75.59 min contact time, the maximum removal percentages of 92.05% and 94.89% for Pb2+ and Cd2+, respectively, were achieved. Langmuir isotherm gave the best fit with values of monolayer uptake capacities as 9.74 mg/g and 14.17 mg/g for Pb2+ and Cd2+, respectively, and pseudo-second-order kinetic model gave the best fit with the adsorption data. [ABSTRACT FROM AUTHOR]

Abstract The pollution of water has been one of the greatest problems faced by the modern society, due to industrialization and urban growth. Rivers, lakes and seas have been continually suffering from the rising concentration of various pollutants, especially toxic elements. This study aimed to evaluate the use of cashew nut shell (Anacardium occidentale) (CNS), after chemical modification with H2O2, H2SO4 and NaOH, as an new and renewable adsorbent material, for the removal of metals Cd2+, Pb2+ and Cr3+ in aqueous medium. The adsorbents were characterized by its chemical constitution, structure, infrared spectroscopy, morphology, by means of scanning electron microscopy, determination of the point of zero charge, thermogravimetrical analysis and porosimetry assessments. Tests were conducted to determine the optimal conditions (pH vs. adsorbent mass) for adsorption, by means of multivariate analysis using a central composite design. The adsorption kinetics was evaluated by models of pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion, while adsorption isotherms were linearized by Langmuir, Freundlich and Dubinin–Radushkevich. The effect of initial concentration, temperature and desorption was also performed. The adsorbents exhibited irregular, spongy and heterogeneous structure. FTIR analysis confirms the presence of hydroxyl, aliphatic, phenolic and carboxylic acid groups, which are favorable adsorption characteristics. The pHPZC of adsorbent is 4.35, 2.50 e 6.92, respectively, for CNS H2O2, H2SO4 and NaOH. The optimum adsorption conditions were as follows: pH 5.0; relation of adsorbent mass/volume of water: 4 g L−1; 40 min of contact time for reaching the equilibration. Results suggest the predominance of chemisorption of Cd2+ and Cr3+. Most of biosorbents exhibited good fit by Langmuir and Freundlich, suggesting the occurrence of adsorption on mono- and multilayers. The adsorbents of cashew nut shell exhibited high removal efficiency of Cd, Pb and Cr from waters.

Interactions between microorganisms and clay minerals influence the transport and cycling of metal contaminants in both marine and terrestrial environments. The present study was conducted to quantify the adsorption of dissolved cadmium, Cd(II), under seawater-like conditions to the marine cyanobacterium Synechococcus sp. PCC 7002, three common clay minerals (kaolinite, montmorillonite and illite), as well as cell-clay aggregates. We show here that the Synechococcus -only experiments removed the most Cd above pH 5.5, followed in decreasing order by aggregates of 50% cells:50% individual clays, aggregates of cells and all 3 clays, and individual clays. Electron microscope imaging showed that clays associated in a tangential edge-on orientation to the cells in Synechococcus -clay mineral aggregates. A non-electrostatic surface complexation modeling approach was used to fit Cd adsorption onto Synechococcus cells and individual clay minerals. The resulting Cd binding constants were then used in consort with surface functional group p K a values and site concentrations to accurately predict the extent of Cd adsorption onto the Synechococcus -clay mineral aggregates using the component additivity (CA) approach. We observed that the addition of cyanobacterial cells to clay mineral suspensions led to significantly larger mean aggregate sizes of clay minerals, enhancing the clay sedimentation rate. Although specifically focused on Cd, our study indicates that the ratio of bacterial plankton to clay minerals is an important determinant in terms of understanding the rate with which metals are transferred from the water column to the seafloor. [ABSTRACT FROM AUTHOR]

We investigated the adsorption of heavy metal ions on a nanostructured coating of zinc‐aluminum layered double hydroxides (Zn‐Al LDHs) grown on aluminum foam by one‐step hydrothermal process. This approach aimed to increase the interactive surface and provide a more practical medium for removal of toxic heavy metals from aqueous media. The foam coated with LDH was characterized by using scanning electron microscopy and X‐ray diffraction. After immersion in a copper‐rich water solution, X‐ray photoelectron spectroscopy demonstrated the occurrence of adsorbed copper on the LDH‐coated foam with two oxidation states: particles of metallic copper Cu0 with oxidized surface Cu+1. X‐ray diffraction showed the presence of Cu+2 in the LDH structure. [ABSTRACT FROM AUTHOR]

The preparation of two cyclens both possessing two triethoxysilyl groups through click chemistry is described. These two cyclens were incorporated into bis(triethoxysilyl)ethenylene‐based periodic mesoporous organosilica nanoparticles (PMO NPs) at different proportions of bis(triethoxysilyl)ethenylene/cyclens (90/10, 75/25). The obtained nanorods were analyzed with different techniques and showed high specific surface areas at low proportion of cyclens. The nanorods containing free amino groups of cyclen were then used for Ni(II) and Co(II) removal from model solutions. The kinetics and isotherms of adsorption of Ni(II) and Co(II) were determined, and the materials showed high uptake of metals (up to 3.9 mmol ⋅ g−1). They demonstrated pronounced selectivity in separation of rare earth elements from late transition metals, e. g. Ni(II) and Co(II) by adsorption and even more so by controlled desorption. [ABSTRACT FROM AUTHOR]

Pressmud is one of the most abundant wastes produced in the sugarcane industry; however, far too little attention has been paid to it as a reactive material for pollutant removal. This paper investigates the potential use of the composted pressmud for Cd2+ removal and considers the possible remobilization of the ion after the use and subsequent disposal of this material. Characterization and adsorption analyses (batch equilibrium and kinetic) were carried out in addition to desorption and bioaccessibility assays. The pressmud revealed promising adsorption characteristics, including a high specific surface area (SSA) (236.1 m2 g−1) and the presence of oxygen surface functional groups. The batch equilibrium data exhibit a better fit with the Langmuir isotherm model, assuming a monolayer adsorption capacity of 12.063 mg g−1, and for kinetic data, the pseudosecond-order model satisfactorily suited the adsorption. The equilibrium time was attained rapidly at lower concentrations (within 30 min), increasing to 180 min at 500 mg L−1, due to the contribution of the intraparticle diffusion process. According to the desorption and bioaccessibility tests, pressmud is capable of maintaining the element at the binding sites, although the Cd2+ adsorbed by the material is almost in its bioaccessible form, which supports the need of the correct handling after use. The results indicate that pressmud may be a promising reactive material for Cd2+ adsorption, identifying upcycling opportunities for this low-cost and renewable waste. [ABSTRACT FROM AUTHOR]

A novel mesoporous chitin blended MoO 3 -Montmorillonite nanocomposite was prepared through three-steps synthesis. First, chitin was extracted from prawn shell then MoO 3 -MMT was prepared, and lastly, chitin was blended with MoO 3 -MMT. Chitin-MoO 3 -MMT was applied for the removal of Cu(II) and Pb(II) from wastewater. XRD characterization revealed MoO 3 solubility in MMT interlayers, SEM showed a nanocomposite formation with sharp nanorods like-structure and length ranging from 60 to 77.7 nm. FTIR exhibited fundamental changes in the surface functional groups after adsorption. XPS analysis before and after adsorption showed the domination of chemical bonding with N and O. N 2 adsorption-desorption isotherm displayed H 3 -type hysteresis loop and a pore size diameter of 10.67 nm confirming the mesoporous nature. Adsorption efficiency was studied as a function of pH, time, metal concentration and adsorbent mass. Adsorption capacity (Q e) values were 19.03 and 15.92 mg.g−1 for Cu(II) and Pb(II) respectively. The metal surface coverage mapping was 1.87 × 10^19 and 4.34 × 10^18 atoms/m2 for Cu(II) and Pb(II) respectively. Adsorption followed Langmuir isotherm and pseudo-second-order (PSO) kinetics suggesting a monolayer chemisorption domination. Intraparticle diffusion (IPD) model showed a boundary layer control. Thermodynamically, the adsorption was spontaneous and endothermic with activation energies 25.94 and 29.37 kJ.mol−1 for Cu(II) and Pb(II) respectively. Unlabelled Image • Novel chitin/MoO 3 /montmorillonite nanocomposite for Cu2+ and Pb2+ removal. • The nanocomposite was characterized using XRD, XPS, SEM, FTIR, BET and zetasizer. • The nanocomposite exhibited a mesoporous nanorod like-structure. • Adsorption surface coverage was mapped in terms of adsorbed atoms/m2. • Adsorption modelling was studied and assessed by ANOVA statistical test. [ABSTRACT FROM AUTHOR]

Hybrid materials of conducting polymers with coordination compound dopants offer a desirable combination of properties for targeted applications. This work presents polythiophene/prussian red (PTH/PR) nanocomposites as hybrid materials using PTH as a polymer matrix and PR nanoparticles as a readily available dopant with photo-reactive and magnetically active low-spin iron(III) complex. The PTH/PR nanocomposite was prepared by oxidative polymerization of thiophene monomers in the presence of PR nanoparticles. The synthesized material is characterized using Fourier transform infrared spectroscopy, powder x-ray diffraction and transmission electron microscopy. Comparative studies of the PTH/PR nanocomposite indicate an enhancement in thermal and electrical properties compared with other PTH nanocomposites. The investigated physicochemical properties of PTH/PR suggest its suitability as a material for environmental applications, which were explored through dye photodegradation and metal ion recovery via adsorption studies. The PTH/PR nanocomposite degraded 65% of a methylene blue dye within 100 min by photo-oxidation, following pseudo-first-order kinetics. It also displayed good adsorptive tendency towards precious metal ions including Au(III), Cu(II), Pd(II) and Ag(I). This finding suggests that PTH/PR nanocomposites could constitute potent nanomaterials for water treatment. [ABSTRACT FROM AUTHOR]

Biochar prepared from waste biomass was evaluated as a soil amendment to immobilize metals in two contaminated soils. A 60-day incubation experiment was set up on a French technosol which was heavily contaminated with Pb due to former mining activities. Grass biochar, cow manure biochar (CMB) and two lightwood biochars differing in particle size distribution (LWB1 and LWB2) were amended to the soil at a rate of 2% (by mass). Rhizon soil moisture samplers were employed to assess the Pb concentrations in the soil solution at regular times. After 30 days of incubation, soil solution concentrations in the CMB-amended soil decreased by more than 99% compared to the control. CMB was also applied to a moderately contaminated Flemish soil and resulted in lowered soil solution Cd and Zn concentrations. While the application of 4% CMB resulted in 90% and 80% reductions in soil solution concentrations of Cd and Zn, respectively, the solid fraction of digestate (as a reference) reduced the soil pore water concentrations by only 63% for Cd and 73% for Zn, compared to the concentrations in the control. These results emphasize the potential of biochar to immobilize metals in soil and water systems, thus reducing their phytotoxicity. [ABSTRACT FROM AUTHOR]

The adsorption of metal onto archaea could affect metal behavior and bioavailability in hypersaline environments where archaea represent the dominant life form. However, the mechanism and thermodynamics of metal adsorption onto halophilic archaea are not well understood. In this study, Cd adsorption experiments and potentiometric titrations were conducted to model metal adsorption by the halophilic archaeon Halobacterium sp.. Cd adsorption onto the archaeal cells exhibits slow adsorption kinetics, taking 8 h to reach steady-state. The extent of Cd adsorption depends strongly on pC H+ and Cd loading. Desorption of Cd is even slower than adsorption, but exposure of the Cd-adsorbed biomass to high concentrations of cysteine promotes desorption and demonstrates that the distribution of Cd is controlled by reversible adsorption reactions, likely involving sulfhydryl binding of Cd on the cell surface. We conducted potentiometric titration experiments with and without sulfhydryl site blocking to yield a total sulfhydryl site concentration of 91 ± 28 μmol/g within the archaeal cell envelope. Using a combination of the X-ray absorption fine structure analysis results from Showalter et al. (2016) and the Cd adsorption measurements and titration data from this study, we construct a surface complexation model of the Cd adsorption behavior. Because the Cd adsorption behavior is likely similar to that of a range of chalcophilic micronutrients, the importance of Cd-sulfhydryl binding suggests that the production of high affinity sulfhydryl binding sites by the archaea may represent an adaptive strategy for halophiles to obtain metal nutrients in environments in which aqueous metal-chloride complexation dominates the speciation for many metals. [ABSTRACT FROM AUTHOR]